1. Field of the Invention
The present invention relates to an apparatus for latching to any of a number of electrical apparatuses having differently located centers of gravity for the purpose of lifting the apparatus, particularly for installation in and removal from switchgear cabinets.
2. Background Information
Often, several electrical switching apparatuses, such as circuit breakers, network protectors, disconnect switches and transfer switches, are arranged in a stackable arrangement within a switchgear cabinet or similar electrical panel box. Typically, the switchgear cabinets are divided into cells having "draw-out rails" in which the electrical switching apparatuses, which may weigh several hundred pounds, are received for placement within the appropriate cell within the switchgear cabinet.
Usually it is necessary to utilize a mechanical lifting means, such as a crane, to lift or hoist the larger and heavier electrical switching apparatuses into the draw-out rails for placement within the switchgear cabinet. Furthermore, it is usually necessary to utilize an apparatus for attaching to the electrical switching apparatus being lifted which in turn may be connected to the crane for lifting. When utilizing such an apparatus for attaching to and lifting a particular electrical switching apparatus, it is important that the electrical switching apparatus remain generally level during lifting, i.e. without excess tilting. If not, then binding may occur when placing the electrical switching apparatus into the draw-out rails resulting in the electrical switching apparatus not being received in the proper position or orientation for placement within the switchgear cabinet. In addition, excess tilting or failure to maintain the electrical switching apparatus generally level during lifting may result in the electrical switching apparatus becoming disconnected from the apparatus attached thereto for lifting the same and possibly resulting in damage to the electrical switching apparatus or personal injury to workers overseeing the lifting operation.
One such known apparatus for attaching to the electrical switching apparatuses for lifting the same is referred to as a "spreader bar." The spreader bar employs conventional hooks on the ends thereof for attaching to and lifting electrical switching apparatuses, and is particularly well suited for attaching to electrical switching apparatuses having a metal frame or metal housing construction. For these type of apparatuses, a lift point is punched in the metal frame or metal housing. The lift point is punched at a location according to the size of the electrical switching apparatus, i.e., for different size apparatuses there is a difference in the weight distribution and thus a difference in the location of the center of gravity of the apparatuses. This enables the different apparatuses to be lifted while being maintained generally level without excess tilting thereof and thus reducing the possibility of improper placement in the switchgear cabinet or the apparatus becoming disconnected from the spreader bar.
While punching lift points in the metal frame or metal housing electrical switching apparatuses in order to attach the spreader bar thereto for even lifting works well and is convenient for these type apparatuses, this technique does not work well for electrical switching apparatuses having other types of frames or housings, such as, for example, a molded housing. For example, electrical switching apparatuses having a range of current ratings can be housed in a standardized molded housing resulting in apparatuses with differently located centers of gravity but with the same lifting points. Tooling limitations in constructing molded housing apparatuses prevent different lifting points being formed in the standardized molded housing for the apparatuses with a range of current ratings, thus necessitating that the same lifting points be used for all apparatuses. This results in the apparatus not being maintained generally level during lifting due to the differently located centers of gravity.
There is a need, therefore, identified for an apparatus for latching to electrical switching apparatuses for purposes of lifting the same, and particularly there is a need identified for an apparatus that is suitable for latching to electrical switching apparatuses having a molded housing construction.
There is a further need for such an apparatus that may be utilized with a family of circuit breakers having a range of current ratings.
There is also a need for such an apparatus that may be utilized for latching to any selected one of a family of electrical switching apparatuses having differently located centers of gravity such that the particular electrical switching apparatus being lifted may be maintained generally level, i.e., without excess tilting thereof.
There is an additional need for such an apparatus that may be easily latched to and unlatched from an electrical switching apparatus to be lifted.
There is yet a further need for such an apparatus that may be securely latched to an electrical switching apparatus so as to reduce the possibility of the electrical switching apparatus becoming disconnected therefrom during lifting.